Means of measuring the magnitude of torque strain set up in a mass of material



Aprll 21, 1953 J. E. WHITE 2,635,465

MEANS OF MEASURING THE MAGNITUDE OF TORQUE STRAIN SETUP IN A MAss OFMATERIAL Filed Aug. 15, 1949 l I I 2| 27 23 INVENTOR.

AWTOENEV Patented Apr. 21, 1953 UNITED STATES PATENT OFFICE MEANS OFMEASURING THE MAGNITUDE OF TORQUE STRAIN SET UP IN A MASS OF MATERIALJud E. White, Long Beach, Calif., assignor to Martin-Decker Corporation,

Long Beach,

4 Claims. 1

This invention relates to a means of measuring the magnitude of torquestrain set up in a mass of material.

In the operation of testing the strength of an article and inascertaining the torque strain to which an article is being subjected itis desirable to provide some simple means for measuring and indicatingthis strain when the article being measured is in operation withoutinterrupting the operation. It is the principal object of the presentinvention therefore to provide means for sensing torque impulsesoccurring in a mass of material and for accurately indicating orrecording the magnitude of these impulses.

The present invention contemplates the provision of means whereby anelement may be secured to a mass of material in a relatively immovablezone and whereby another element may be secured to a mass of material ina movable zone subjected to torque strain. The relatively fixed andmovable elements being associated with pneumatic sensing means wherebythe magnitude of torque in the mass may be detected and measured eitherby visual indicating means or mechanical recording means.

The present invention is illustrated :by way of example in theaccompanying drawings in which:

Figure 1 is a fragmentary view in central longitudinal section showingthe application of the present invention to a drive shaft such as adrive shaft of a well drilling rotary table.

Fig. 2 is a view in end elevation showing the testing tool with whichthe present invention is concerned as seen on the line 22 of Fig. 1.

Fig. 3 is a view in section and elevation as seen on the arcuate line 33of Fig. 2 and indicates a sensing cam contour and a nozzle associatedtherewith.

It is to be understood that the present measuring instrument may beemployed in measuring torque magnitude exerted in any mass. However, inthe present instance the invention is illustrated and described as beingused on the drive shaft of a rotary well table. It will of course beunderstood that this is only one example of the uses to which thestructure of the invention may be put and the method practised,

Referring more particularly to the drawing, III indicates the mainbearing of a rotary well table within which a drive shaft II isrotatably supported. Mounted upon this drive shaft is a suitable drivenmember, such for example as a sprocket wheel I2. The rotation of theshaft Ii by the power applied by the sprocket tends to create torque inthe shaft and it is the object of the present invention to measure themagnitude of this torque. It will be understood that the invention maybe applied to any mass which tends to resist rotation and to which poweris applied tending to produce rotation and to set up torque strainwithin the mass. In order to practise the invention it is desirable todrill a hole I3 longitudinally of the shaft I I. The end of the hole orbore I3 is reduced in diameter at I4 and is internally threaded. Heldwithin the bore I3 and terminating at a shoulder I5 is a bushing I6. Thebushing I6 is tubular and terminates at its outer end in a flange IL.The flange abuts against the end of the shaft I I and is secured inposition by cap screws and bolts I8 which are threaded into bores I9formed in the end of the shaft II. Extending through the bushing I6 andterminating in the threaded end 20 is a sensing shaft 2 I. The majorlength of the shaft is provided with a rotating fit within the bushing I6 by which bushing the shaft is held against lateral movement. It isintended that the length of the shaft 2] shall be greater than thelength of the bushing IB so that it will extend beyond the end of thebushing flange I! and will also be threaded into the threaded bore i l.Furthermore, it is to be pointed out that the section modulusof theportion of the shaft I I with relation to that of the sensing shaft 2!is such as to insure that torque force applied to the relatively tubularend of the shaft I I willproduce gyration while the sensing shaft 2|,which is fixed to the relatively solid mass of the drive shaft II by thethreaded section 20 and threaded bore I4, will be relatively devoid ofany moment of gyration. Thus when torque force is applied to therelatively tubular end of the drive shaft II this end of the drive shaftmay have a slight gyrating motion while the sensing shaft 2| remainsrelatively motionless. It is of course understood that the two shaftsare considered broadly to rotate in unison when driven through thesprocket I 2.

The end of the sensing shaft 2! is designed to extend beyond the end ofthe flange I? on the bushing I6. This end is preferably formed with acam member or disk 22. The cam disk may have a peripheral cam face, orthe cam may be formed as a disk with a suitable cam face 23 protrudingfrom the face of the disk. The contour of the cam face may be shaped asindicated in Fig. 3 01 the drawings where the face is formed with agradually projecting swell portion terminating at its opposite end inthe end plane of the cam disk 22. It is understood that as here shownthe end face of the disk is in the plane normal to the longitudinal axisof the sensing shaft 2|. The device may also be constructed so that thecam disk 22 is inclined to the normal plane of the longitudinal axis ofthe sensing shaft, thus providing a structure having the functions of awell known mechanical element called a wobble plate. In any event theperipheral or projecting surface 23 of a cam carried by the cam disk 22is intended to move toward or away from the discharge end of a nozzle24. The nozzle 24 is here shown as mounted within a bracket or housing25 which is fixed to the end of the drive shaft I I by screws 26 andwhich embraces the projecting end of the sensing shaft 2! and its camdisk 22. The nozzle is connected to a feed pipe and is formed with arestricted orifice which projects a jet of air under pressure againstthe cam face 23 of the cam. This nozzle is connected by a conduit 21 toa pipe 21' which in turn connects with the source of fluid underpressure through a supply pipe 28 with an air compressor bracket (notshown) through a rotary seal 28'. The end of the pipe 21' at a pointbeyond the connection of the conduit 2! therewith is closed. The airunder compression delivered through the pipe therefore is forcedoutwardly through the nozzle and a jet of air impinges against thesurface of the cam shoulder 23. It is obvious that the closer the camshoulder is to the discharge end of the nozzle the greater will be theback pressure built up in the supply pipe 23. This pressure is indicatedby a gauge 29 which is of usual construction and will indicate anyvariation in back pressure which is produced by change in relationshipof the face 23 of the cam disk 22 with the nozzle 24. If desired aconduit 30 may be connected with the supply pipe 28 at a point betweenthe source of fluid under pressure and the gauge 29 so that a supply ofair will be provided to a recording gauge 3! which may be of any desiredtype. It is also desirable to interpose a flow bean or restrictedorifice 30' between the inlet end of pipe 28 and pipe 39. An air filteror pressure reducer may be used if desired.

In order to practise the present invention, for example in testing thetorque strain created in a rotary table drive shaft, the hole [3 isdrilled longitudinally of the shaft I! and a threaded bore I4 is formedat the inner end thereof. The bushing I6 is then placed within the borel3 and is secured by screws l8 which pass through the flanges I! of thebushing. The sensing shaft 2| is then positioned within the bushing l6and its end 20 is screwed into the threaded bore M. The bracket orhousing 25 is then fastened in posi tion by the screws 26 so that thenozzle 24 will register with the cam 23. Power is delivered to thesprocket 12 through some suitable connection, it being understood thatany other type of drive may be used to impart rotation to the shaft. Airunder pressure is then delivered from a pressure source through thesupply pipe 28. In actual practice air at 20 p. s. i. is delivered tothe pipe 28. As will be seen in Fig. l of the drawings, the pipe 28 isdivided into two sections which are connected by a rotating coupling 28.It is obvious that the pipe 2'! and the drive shaft H should belongitudinally aligned so that the shaft and pipe will have a commonaxis. The shaft Il may then rotate around this axis and will at the sametime carry the housing 25 with it, and will rotate the sensing shaft 2|.Due to the load which is imposed upon the main body of the drive shaftII, which shaft portion is substantially rigid, and due to the fact thatthere is less rigidity in the end portion of the drive shaft ll withinwhich the bore I3 occurs, it is obvious that there will be a lag inrotational movement between the cam disk 22 and the housing 25 and itsnozzle 24. This will cause the discharge end of the nozzle to move alongthe surface of the cam face 23 and will result in varying the backpressure created in the supply pipe 28. The magnitude of the backpressure will be indicated by a movement of the hand on the gauge 29. Itis obvious that the dial of the gauge may be calibrated so that asuitable measurement may be indicated, which measurement will at thesame time indicate the amount of torque stress set up in the shaft llunder a given load and with the predetermined application of power.

Due to the fact that the supply pipe 28 accumulates a back pressure bythe operation of the nozzle 24 and the cam 23, and for the furtherreason that the restricted member 6 acts so that the nozzle orifice willnot allow enough airflow to build up a back pressure in pipe 28 and atthe other end of the pipe 23 when the nozzle 24 is closed, this willinsure that the escape of air is insignificant as compared with theairflow through the orifice of the nozzle 24. This results in buildingup the back pressure almost to the value of the supply pressure.

It will thus be seen that the structure here disclosed is decidedlysimple in its construction and operation, and that by its use it ispossible to ascertain torque resistance and torque strains set up in amass of material which will be indicated by a visual reading orrecording.

While I have shown a preferred apparatus embodying my invention, it isto be understood that various changes might be made in the combinationof elements shown for practising the invention by those skilled in theart without departing from the spirit of the invention as claimed.

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

1. Means for measuring the torque strain set up in a rotary shaft, oneend of which shaft is restrained by a load and to the other end of whichshaft torque driving force is applied, said shaft being formed at itsdriving end with a central bore whereby the driving end will have alesser torque moment than the driven end, a cam shaft extending freelyinto said bore and fixed to the mass of the shaft contiguous to the loadbearing end, a support fixed upon the end of the drive shaft to rotatewith the shaft around its longitudinal axis, a cam carried by the camshaft in a position beyond the end of the drive shaft, a nozzle carriedby the support and formed with a discharge orifice which is locatedeccentrically of the axis of rotation of the shaft, said cam having acontour whereby relative rotary movement between the nozzle and the camwill change the spacing between the discharge orifice of the nozzle andthe surface contour of the cam, means for delivering fluid underconstant pressure to said nozzle continuously, and pressure responsivemeans indicating variation in pressure occurring within the deliverymeans as produced by back pressure caused by variation in the spacingbetween the nozzle orifice and the cam contour.

2. A device for measuring the torque strain set up in a shaft betweentwo points at one of which points a torque driving force is applied tosaid shaft, and at the other of which points a torque load is applied tosaid shaft to resist the rotation thereof, said device comprising: asubstantially torque free member fixed at one end thereof to said shaftat one of the said points and extending parallel to and concentric withsaid shaft to the other of said points, a support member fixed upon saidshaft adjacent said other point, a cam provided on one of said membersand concentrically related to said shaft and having a face the contourof which slopes away from a plane surface of rotation formed about theaxis of said shaft, a nozzle carried by the other member and having adischarge orifice aligned to bear on said cam face whereby a jetdischarged from said orifice will impinge upon said face and thetwisting of said shaft will cause a variation in the space between themouth of said orifice and said cam face, means for delivering fluidunder constant pressure to said nozzle, and pressure responsive meansindicating variations in pressure occurring within said fluid deliverymeans and produced by variations in the back pressure caused by saidorifice being spaced diflerent distances from said cam face.

3. A combination as in claim 2 in which said nozzle is mounted with itsorifice parallel with the axis of said shaft, and in which said cam isin References Cited in the file of this patent UNITED STATES PATENTSNumber Name Date 2,044,461 Beck June 16, 1936 2,150,377 Keinath Mar. 14,1939 2,268,733 Tate Jan. 6, 1942 2,329,121 Lamberger et al. Sept. '7,1943 2,358,894 Volet Sept. 26, 1944 2,455,285 Versaw Nov. 30, 1948

